Logical Block Addressing

When we need to read a certain sector from the hard disk drive, we need to know its physical location, i.e. its cylinder, head and sector inside the track. LBA mode was developed in 1993 and it assigns a unique number to each sector on the hard disk drive, making it easier to access each hard disk drive sector. In LBA mode, instead of accessing each sector by addressing its physical location (cylinder, head and sector, also known as CHS) we access each sector using this unique number. For example, instead of asking for the data stored in sector 62, cylinder 33, head 2, it is easier to ask for the data stored in sector 806.

LBA mode allowed to PCs to have hard disk drives greater than 504 MB. Before 1993 PCs couldn’t access directly hard drives over this capacity because they didn’t have LBA mode.